Distributed Bragg reflector–based resonance filters for silicon photonics: design and demonstration

We review the design and demonstration of distributed Bragg reflector (DBR)-based resonance filters developed at CoE-CPPICS, IIT Madras, with the in-house complementary metal oxide semiconductor (CMOS)-compatible silicon photonics technology platform. The proposed devices include two types of band-pass filter design approaches, i.e., the higher-order DBR coupled cavity filter and apodized DBR cavity filter with ultra-broad stopband for guided Fabry–Pérot resonance in a silicon-on-insulator rib waveguide structure. The device design parameters are optimized through semi-analytical simulation methods for a low insertion loss singly resonant transmission peak at a desired wavelength. Fourth- and fifth-order passive resonant filters are designed and demonstrated with nearly lossless, flat-top response (ripple <1 dB) with large out-of-band rejection (>40 dB), and a maximum shape factor of 0.9 without any active tuning. With optimized apodization parameters for the DBR cavity, a device of length as low as ∼35μm exhibits a large rejection band of ∼60 nm and an extinction of ∼40 dB at the resonant wavelength peak at λr∼1550 nm (FWHM ∼80 pm, IL ∼2 dB). The demonstrated devices are potential candidates for many integrated photonic applications such as microwave filters, modulators, add-drop multiplexers, sensors, and broadband noise suppression.